In an accademic essay, the thesis statement is usually a single sentence somewhere in your first paragraph that presents your argument to the reader. The rest of the paper, the body of the essay, gathers and organizes evidence that will persuade the reader of the logic of your interpretation.
Every major paragraph that follows then requires its own topic sentence. The topic sentence encapsulates the meaning of that paragraph.
When we organize in this way, it helps us to remember to start a new paragraph when we start mentioning things that no longer relate directly to that paragraph's topic sentence, and to start a new essay when we start including paragraphs that do not relate to the thesis statement.
This academic style is not often used for informal typing, or journalistic (newspaper) style. Informal and journalistic style encourages more frequuent paragraph breaks, often to make it easier to "keep your place" in the story. Newspaper columns, for example, are so narrow that a long paragraph would extend for several inches, and lose the reader.
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